This is pdfTeX, Version 3.1415926-2.5-1.40.14 (TeX Live 2013/Debian) (format=pdflatex 2016.3.8)  21 SEP 2017 15:39
entering extended mode
 restricted \write18 enabled.
 %&-line parsing enabled.
**sentry456_summary.tex
(./sentry456_summary.tex
LaTeX2e <2011/06/27>
Babel <3.9h> and hyphenation patterns for 78 languages loaded.
! Undefined control sequence.
l.1 \subsection
               {sentry456 Summary}
? 
! Interruption.
<to be read again> 
                   {
l.1 \subsection{
                sentry456 Summary}
? exit
 
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 173 string characters out of 6139872
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 3640 words of font info for 14 fonts, out of 8000000 for 9000
 957 hyphenation exceptions out of 8191
 5i,0n,1p,59b,8s stack positions out of 5000i,500n,10000p,200000b,80000s
No pages of output.
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 1 words of extra memory for PDF output out of 10000 (max. 10000000)